// This is an open source non-commercial project. Dear PVS-Studio, please check it.
// PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com

// ReSharper disable CheckNamespace
// ReSharper disable CommentTypo
// ReSharper disable IdentifierTypo
// ReSharper disable InconsistentNaming
// ReSharper disable UnusedMember.Global

/*
 * Ars Magna project, http://arsmagna.ru
 */

#nullable enable

namespace PdfSharpCore.Pdf.Advanced;

/// <summary>
/// Represents a PDF soft mask.
/// </summary>
public class PdfSoftMask
    : PdfDictionary
{
    /// <summary>
    /// Initializes a new instance of the <see cref="PdfXObject"/> class.
    /// </summary>
    /// <param name="document">The document that owns the object.</param>
    public PdfSoftMask (PdfDocument document)
        : base (document)
    {
        Elements.SetName (Keys.Type, "/Mask");
    }

    /// <summary>
    /// Predefined keys of this dictionary.
    /// </summary>
    public class Keys
        : KeysBase
    {
        /// <summary>
        /// (Optional) The type of PDF object that this dictionary describes;
        /// if present, must be Mask for a soft-mask dictionary.
        /// </summary>
        [KeyInfo (KeyType.Name | KeyType.Optional, FixedValue = "Mask")]
        public const string Type = "/Type";

        /// <summary>
        /// (Required) A subtype specifying the method to be used in deriving the mask values
        /// from the transparency group specified by the G entry:
        /// Alpha: Use the group�s computed alpha, disregarding its color.
        /// Luminosity: Convert the group�s computed color to a single-component luminosity value.
        /// </summary>
        [KeyInfo (KeyType.Name | KeyType.Required)]
        public const string S = "/S";

        /// <summary>
        /// (Required) A transparency group XObject to be used as the source of alpha
        /// or color values for deriving the mask. If the subtype S is Luminosity, the
        /// group attributes dictionary must contain a CS entry defining the color space
        /// in which the compositing computation is to be performed.
        /// </summary>
        [KeyInfo (KeyType.Stream | KeyType.Required)]
        public const string G = "/G";

        /// <summary>
        /// (Optional) An array of component values specifying the color to be used
        /// as the backdrop against which to composite the transparency group XObject G.
        /// This entry is consulted only if the subtype S is Luminosity. The array consists of
        /// n numbers, where n is the number of components in the color space specified
        /// by the CS entry in the group attributes dictionary.
        /// Default value: the color space�s initial value, representing black.
        /// </summary>
        [KeyInfo (KeyType.Array | KeyType.Optional)]
        public const string BC = "/BC";

        /// <summary>
        /// (Optional) A function object specifying the transfer function to be used in
        /// deriving the mask values. The function accepts one input, the computed
        /// group alpha or luminosity (depending on the value of the subtype S), and
        /// returns one output, the resulting mask value. Both the input and output
        /// must be in the range 0.0 to 1.0; if the computed output falls outside this
        /// range, it is forced to the nearest valid value. The name Identity may be
        /// specified in place of a function object to designate the identity function.
        /// Default value: Identity.
        /// </summary>
        [KeyInfo (KeyType.FunctionOrName | KeyType.Optional)]
        public const string TR = "/TR";
    }
}
